Thermal infrared properties of classical and type II Cepheids Diffraction limited 10 microns imaging with VLT/VISIR

Abstract

We present new thermal IR photometry and spectral energy distributions (SEDs) of eight classical Cepheids (type I) and three type II Cepheids, using VISIR thermal IR photometric measurements, supplemented with literature data. We used the BURST mode of the instrument to get diffraction-limited images at 8.59, 11.25 and 11.85 μm. The SEDs show a IR excess at wavelengths longer than 10μm in ten of the eleven stars. We tentatively attribute these excesses to circumstellar emission created by mass loss from the Cepheids. With some hypotheses for the dust composition, we estimated a total mass of the envelope ranging from 10-10 to 10-8 M\odot. We also detect a spatially extended emission around AX Cir, X Sgr, W Sgr, Y Oph and U Car while we do not resolve the circumstellar envelope (CSE) for the other stars. The averaged circumstellar envelope brightnesses relative to the stellar photosphere are α(AX Cir) = 13.8\pm2.5%, α(X Sgr) = 7.9\pm1.4%, α(W Sgr) = 3.8\pm0.6%, α(Y Oph) = 15.1\pm1.4% and α(U Car) = 16.3\pm1.4% at 8.59 μm. With this study, we extend the number of classical Cepheids with detected CSEs from 9 to 14, confirming that at least a large fraction of all Cepheids are experiencing significant mass loss. The presence of these CSEs may also impact the future use of Cepheids as standard candles at near and thermal infrared wavelengths.

References in corpus (14)

• The AKARI/IRC Mid-Infrared All-Sky Survey
• The influence of chemical composition on the properties of Cepheid stars. II-The iron content
• A new calibration of Galactic Cepheid Period-Luminosity relations from B to K bands, and a comparison to LMC PL relations
• The Luminosities and Distance Scales of Type II Cepheid and RR Lyrae variables
• High resolution spectroscopy for Cepheids distance determination. I. Line asymmetry
• On the Enhancement of Mass Loss in Cepheids Due to Radial Pulsation
• Extended envelopes around Galactic Cepheids III. Y Oph and alpha Per from near-infrared interferometry with CHARA/FLUOR
• An Infrared Nebula Associated with Delta Cephei: Evidence of Mass Loss?
• Baade-Wesselink distances and the effect of metallicity in classical cepheids
• Galactic Cepheids with Spitzer: II. Search for Extended Infrared Emission
• Dust-grain processing in circumbinary discs around evolved binaries. The RV Tauri spectral twins RU Cen and AC Her
• The environment of the fast rotating star Achernar - High-resolution thermal infrared imaging with VISIR in BURST mode
• Testing Mass Loss in Large Magellanic Cloud Cepheids using Infrared and Optical Observations II. Predictions and Tests of the OGLE-III Fundamental-Mode Cepheids
• Spatially extended emission around the Cepheid RS Puppis in near-infrared hydrogen lines. Adaptive optics imaging with VLT/NACO

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• A Global Physical Model for Cepheids
• Observational calibration of the projection factor of Cepheids IV. Period-projection factor relation of Galactic and Magellanic Cloud Cepheids
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• Extended envelopes around Galactic Cepheids IV. T Monocerotis and X Sagittarii from mid-infrared interferometry with VLTI/MIDI
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• Multiplicity of Galactic Cepheids from long-baseline interferometry. II. The Companion of AX Circini revealed with VLTI/PIONIER
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